Internal combustion engine

ABSTRACT

An internal combustion engine is provided. The internal combustion engine includes a control device, and at least one injector for liquid fuel. The injector(s) can be controlled by the control device via an actuator control signal. The injector(s) include an injector outlet opening for the liquid fuel which can be closed by a needle. A sensor is also provided for measuring a measurement variable of the injector(s). The sensor is or can be in a signal connection with the control device. An algorithm is stored in the control device, which algorithm calculates a state of the injector(s) based on input variables and an injector model, compares the state calculated via the injector model with a target state, and produces a state signal in accordance therewith. The state signal is characteristic of a change in the state of the injector(s) that occurs during intended use of the injector(s) and/or an unforeseen change in the state of the injector(s). The input variables include at least the actuator control signal and the measurement values of the sensor. A method for operating such an internal combustion engine and an injector is also provided.

This invention relates to an internal combustion engine with thefeatures of the preamble of claim 1 and a method with the features ofthe preamble of claim 14 or 15.

A class-specific internal combustion engine and a class-specific methodare derived from DE 100 55 192 A1. This publication discloses a methodfor concentricity control of diesel engines, wherein the injectionquantity of the injectors assigned to the cylinders is corrected bymeans of a correction factor.

The problem is that the injectors known from the prior art are replacedafter a certain service life (number of operating hours) without knowingwhether the replacement is even necessary based on the internal state ofthe injector.

The object of the invention is to provide an internal combustion engineand a method in which only those injectors need to be replaced wherethis is necessary due to their internal condition.

This object is achieved by an internal combustion engine with thefeatures of claim 1 and a method with the features of claim 14 or 15.Advantageous embodiments of the invention are defined in the dependentclaims.

An example of the liquid fuel is diesel. It could also be heavy oil oranother self-igniting fuel.

The invention provides that an algorithm is stored in the controldevice, which algorithm calculates a state of the injector on the basisof input variables and an injector model, compares the state calculatedby means of the injector model with a target state, and produces a statesignal in accordance therewith, which state signal is characteristic ofa change in the state of the injector that occurs during intended use ofthe injector (e.g. due to aging and/or wear and tear) and/or anunforeseen change in the state of the injector (e.g. due to damage tothe injector or excessive formation of deposits), wherein the inputvariables comprise at least the actuator control signal and themeasurement values of the sensor.

The control device compares a value at the time of execution of thealgorithm (specified normal value or value from one or more of the lastcombustion cycles) for at least one variable contained in the injectormodel (e.g. pressure progression in one of the volumes or mass flowsbetween adjacent volumes or the kinematics of the needle during aninjection process) with the current estimated value determined by thealgorithm. The state of the injector can be deduced in case of anychange. On the basis of the conclusion, the control device can producethe signal representative of the state of the injector.

If, for example, with constant duration of actuation of the actuator theestimated kinematics of the needle changes so that the needle lifts offthe needle seat slower or faster, the control device interprets this insuch a way that the state of the injector has changed. This can be dueto wear and tear, aging or damage to the injector and the control devicecan (e.g. on the basis of empirical values) determine the remainingservice life of the injector. If the deviation is greater than aspecified target value, the control device can indicate when or that theinjector is to be replaced based on the state signal.

It is preferably provided that the algorithm comprises a pilot controlwhich calculates a pilot control signal for the actuator control signalfrom a desired target value of the amount of liquid fuel and/or a needleposition target value. The pilot control ensures a fast system response,because in case of necessary corrections of the actuator control signalor the pilot control signal, it controls the actuator as if no injectorvariability would exist.

The pilot control uses, for example, an injector map (which, forexample, in the case of an actuator designed as a solenoid valve,indicates the duration of current flow over the injection amount orvolume) or an inverted injector model to convert the target value of theamount of liquid fuel to be injected and/or the needle position targetvalue into the pilot control command.

When the control device is designed with pilot control, it can beparticularly preferably provided that the algorithm comprises a feedbackloop, which, taking into account the actuator control signal calculatedby the pilot control and the at least one measurement variable by meansof the injector model, calculates the amount of liquid fuel dischargedvia the discharge opening of the injector and/or the position of theneedle and, if necessary, (if there is a deviation) corrects the pilotcontrol signal calculated by the pilot control for the actuator controlsignal. The feedback loop is used to correct the inaccuracies of thepilot control (due to manufacturing variabilities, wear, etc.), whichcause an injector drift.

The algorithm has preferably an observer which, using the injectormodel, estimates the injected amount of liquid fuel and/or the positionof the needle depending on the at least one measurement variable and theat least one actuator control signal. An actual measurement of theinjected amount of liquid fuel or the measurement of the position of theneedle is therefore not required for the feedback loop. Regardless ofwhether a feedback loop is provided, the injected amount of liquid fuelestimated by the observer and/or the estimated position of the needle inthe pilot control can be used to improve the actuator control signal.

Various possible formations of the observer are known to the personskilled in the art from the literature (e.g. Luenberger observer, Kalmanfilter, “sliding mode” observer, etc.).

In principle, it is possible to calculate the actuator control signal onthe basis of the target value for the injected amount of liquid fueland/or the position of the needle and on the basis of the amount ofliquid fuel estimated by the observer or the estimated position of theneedle. This gives an adaptive pilot control signal modified by theobserver. In this case, the control is therefore not constructed in twoparts, with a pilot control and a feedback loop correcting the pilotcontrol signal.

It may be provided that the injector model comprises at least:

the pressure progressions in the volumes of the injector filled with theliquid fuel

mass flow rates between the volumes of the injector filled with theliquid fuel

kinematic variables of the needle, e.g. a position of the needle,preferably relative to the needle seat

dynamics of the actuator of the needle, preferably solenoid valvedynamics

The invention makes it possible to monitor selected or all of theabove-mentioned variables over time and, if necessary, to react withmaintenance or replacement of the injector (“condition basedmaintenance”).

The injector may comprise at least:

an input storage chamber connected to a common rail of the internalcombustion engine

a storage chamber for liquid fuel connected to said input storagechamber

a volume connected to the storage chamber via needle seat

a connection volume connected on one side to the storage chamber and onthe other side to a drain line

a discharge opening for liquid fuel, which can be closed by a needle andis connected to the volume via a needle seat

an actuator controllable by means of the actuator control signal,preferably a solenoid valve, for opening the needle

preferably a control chamber connected on one side to the storagechamber and on the other side to the connection volume

The needle is usually preloaded by a spring against the openingdirection.

An injector can be provided, which does not require a control chamber,e.g. an injector in which the needle is controlled by a piezo element.

The at least one measurement variable can be, for example, selected fromthe following variables or a combination thereof:

pressure in a common rail of the internal combustion engine

pressure in an input storage chamber of the injector

pressure in a control chamber of the injector

start of needle lift-off from the needle seat.

The control device may be designed to execute the algorithm during eachcombustion cycle or selected combustion cycles of the internalcombustion engine.

Alternatively, the control device may be designed to execute thealgorithm during each combustion cycle or selected combustion cycles ofthe internal combustion engine.

Alternatively, or in addition to one of the above-mentioned embodiments,the control device may be designed to execute the algorithm during eachcombustion cycle or selected combustion cycles of the internalcombustion engine and to statically evaluate the deviations that haveoccurred.

It is not absolutely necessary for the invention to measure the amountof injected liquid fuel or the position of the needle directly. It isalso not necessary to deduce directly from the at least one measurementvariable the actual injected amount of liquid fuel or the position ofthe needle.

In general, the following applies: Instead of the amount of injectedfuel, it is of course also possible to calculate the volume or othervariables which are characteristic of a certain amount of injected fuel.All these possibilities are covered in this disclosure when using theterm “amount”.

The invention can preferably be used in a stationary internal combustionengine, for marine applications or mobile applications such as so-called“non-road mobile machinery” (NRMM), preferably as a reciprocating pistonengine. The internal combustion engine can be used as a mechanicaldrive, e.g. for operating compressor systems or coupled with a generatorto a genset for generating electrical energy. The internal combustionengine preferably comprises a plurality of combustion chambers withcorresponding gas supply devices and injectors. Each combustion chambercan be controlled individually.

Exemplary embodiments of the invention are explained in more detail bythe figures below. They are as follows:

FIG. 1 a first exemplary embodiment of a first control diagram

FIG. 2 a second exemplary embodiment of a second control diagram

FIG. 3 a first example of a schematic representation of an injector

FIG. 4 a second example of a schematic representation of an injector

FIG. 1:

The object of the injector control in this exemplary embodiment is thecontrol of the actual injected amount of liquid fuel and/or the positionz of the needle to a target value m_(d) ^(ref) or z^(ref), bycontrolling the injection duration or the duration of actuation of theactuator of the needle Δt. The control strategy is carried out by

a pilot control (FF), which consist of a desired target value of theamount m_(d) ^(ref) on liquid fuel and/or a needle position target valuez^(ref) calculates a pilot control signal Δt_(ff) (hereinafter alsoreferred to as “control command”) for the injection duration or theduration of actuation of the actuator and

a feedback loop (FB) which, using an observer 7 (“state estimator”),taking into account the pilot control signal Δt_(ff) calculated by thepilot control and at least one measurement variable y (e.g. one of thepressure progressions p_(1A), p_(cc), p_(JC), p_(AC), p_(SA) occurringin the injector or the start of the needle lift-off from the needleseat), the mass flow {circumflex over (m)}_(d) of liquid fuel dischargedvia the discharge opening of the injector and/or the position of theneedle {circumflex over (z)} estimated by means of the injector modeland, if necessary, corrects the pilot control signal Δt_(ff) calculatedby the pilot control by means of a correction value Δt_(fb). Theobserver also outputs the state signal C.

The pilot control ensures a fast system response, since it controls theinjector with an injection duration Δt as if no injector variabilitywould exist. The pilot control uses a calibrated injector map (whichindicates the duration of current flow over the injection amount orvolume) or an inverted injector model to convert the target value of theamount m_(d) ^(ref) of liquid fuel and/or the needle position targetvalue z^(ref) into the pilot control command Δt_(ff).

The feedback loop (FB) is used to correct the inaccuracies of the pilotcontrol (due to manufacturing variabilities, wear, etc.), which cause aninjector drift. The feedback loop compares the target value m_(d) ^(ref)and/or z^(ref) with the estimated injected amount {circumflex over(m)}_(d) of liquid fuel or the estimated position of the needle{circumflex over (z)} and gives as feedback a correction control commandΔt_(fb) (which can also be negative) for the injection duration or theduration of actuation of the actuator, if there is a discrepancy betweenm_(d) ^(ref) and {circumflex over (m)}_(d) or z^(ref) and {circumflexover (z)}. The addition of Δt_(ff) and Δt_(fb) gives the final injectionduration Δt or the duration of actuation of the actuator.

The observer estimates the injected amount {circumflex over (m)}_(d) ofliquid fuel and/or the position of the needle {circumflex over (z)} independence of the at least one measurement variable y and the finalinjection duration Δt or the duration of actuation of the actuator. Theat least one measurement variable can refer to: common rail pressurep_(CR), pressure in the input storage chamber p_(IA), pressure in thecontrol chamber p_(cc) and start of the needle lift-off from the needleseat. The observer uses a reduced injector model to estimate theinjected amount {circumflex over (m)}_(d) of liquid fuel or the positionof the needle {circumflex over (z)}.

FIG. 2

This figure shows a one-piece control, in which the actuator controlsignal Δt is calculated based on the target value m_(d) ^(ref) for theinjected amount of liquid fuel and/or the needle position target valuez^(ref) and based on the parameter Δpar_(mod) used in the pilot controlmodel and estimated by the observer. This gives an adaptive pilotcontrol signal modified by the observer. In this case, the control istherefore not constructed in two parts, with a pilot control and afeedback loop correcting the pilot control signal.

FIG. 3

shows a block diagram of a reduced injector model. The injector modelconsists of a structural model of the injector and an equation system todescribe the dynamic behavior of the structural model. The structuralmodel consists of five modeled volumes: input storage chamber 1, storagechamber 3, control chamber 2, volume over needle seat 4 and connectionvolume 5.

The input storage chamber 1 represents the summary of all volumesbetween the input choke and the non-return valve. The storage chamber 3represents the summary of all volumes from the non-return valve tovolume 4 above the needle seat. The volume 4 over the needle seatrepresents the summary of all volumes between the needle seat to thedischarge opening of the injector. The connection volume 5 representsthe summary of all volumes which connects the storage chamber 3 and thecontrol chamber 2 with the solenoid valve.

FIG. 4 shows an alternatively designed injector which does not requirecontrol chamber 2, e.g. an injector in which the needle 6 is controlledby a piezo element.

The following equation system is not related to the embodiment shown inFIG. 4. The formulation of a corresponding equation system may beanalogous to that shown below.

The dynamic behavior of the structure model is described by thefollowing equation systems:

Pressure Dynamics

The temporal evolution of the pressure within each of the volumes iscalculated based on a combination of the mass conservation law and thepressure density characteristic of the liquid fuel. The temporalevolution of the pressure follows from:

$\begin{matrix}{{\overset{.}{p}}_{IA} = {\frac{K_{f}}{\rho_{IA}V_{IA}}( {{\overset{.}{m}}_{in} - {\overset{.}{m}}_{aci}} )}} & {{Eq}.\mspace{14mu} 1.1} \\{{\overset{.}{p}}_{CC} = {\frac{K_{f}}{\rho_{CC}V_{CC}}( {{\overset{.}{m}}_{zd} - {\overset{.}{m}}_{ad} - {\rho_{CC}{\overset{.}{V}}_{CC}}} )}} & {{Eq}.\mspace{14mu} 1.2} \\{{\overset{.}{p}}_{JC} = {\frac{K_{f}}{\rho_{JC}V_{JC}}( {{\overset{.}{m}}_{bd} + {\overset{.}{m}}_{ad} - {\overset{.}{m}}_{sol}} )}} & {{Eq}.\mspace{14mu} 1.3} \\{{\overset{.}{p}}_{AC} = {\frac{K_{f}}{\rho_{AC}V_{AC}}( {{\overset{.}{m}}_{aci} - {\overset{.}{m}}_{ann} - {\overset{.}{m}}_{bd} - {\overset{.}{m}}_{zd} - {\rho_{AC}{\overset{.}{V}}_{AC}}} )}} & {{Eq}.\mspace{14mu} 1.4} \\{{\overset{.}{p}}_{SA} = {\frac{K_{f}}{\rho_{SA}V_{SA}}( {{\overset{.}{m}}_{ann} - {\overset{.}{m}}_{inj} - {\rho_{SA}{\overset{.}{V}}_{SA}}} )}} & {{Eq}.\mspace{14mu} 1.5}\end{matrix}$

Formula Symbols Used

p_(IA): Pressure in the input storage chamber 1 in bar

p_(cc): Pressure in the control chamber 2 in bar

p_(JC): Pressure in the connection volume 5 in bar

p_(AC): Pressure in the storage chamber 3 in bar

p_(SA): Pressure in the small storage chamber 4 in bar

p_(IA): Diesel mass density within the input storage chamber 1 in kg/m³

p_(CC): Diesel mass density within the control chamber 2 in kg/m³

p_(JC): Diesel mass density within the connection volume 5 in kg/m³

p_(AC): Diesel mass density within the storage chamber 3 in kg/m³

p_(SA): Diesel mass density within the small storage chamber 4 in kg/m³

K_(f): Bulk modulus of diesel fuel in bar

Needle Dynamics

The needle position is calculated by the following equation of motion:

${\begin{matrix} \\\end{matrix}\overset{¨}{z}} = \{ {{\begin{matrix}{{0\mspace{14mu} {if}\mspace{14mu} F_{hyd}} \leq F_{pre}} \\{{\frac{1}{m}( {F_{hyd} - {Kz} - {B\overset{.}{z}} - F_{pre}} )\mspace{14mu} {if}\mspace{14mu} F_{hyd}} > F_{pre}}\end{matrix}F_{hyd}} = {{{p_{AC}A_{AC}} + {p_{SA}A_{SA}} - {p_{CC}A_{CC}}}{0 \leq z \leq z_{\max}}}} $

Z: Needle position in meters (m)

Z_(max): Maximum deflection of the needle 6 in m

K: Spring stiffness in N/m

B: Spring damping coefficient in N·s/m

F_(pre): Spring preload in N

A_(AC): Hydraulic effective area in the storage chamber 3 in m²

A_(SA): Hydraulic effective area in the small storage chamber 4 in m²

A_(CC): Hydraulic effective area in the control chamber 2 in m²

Dynamics of the Solenoid Valve

The solenoid valve is modeled by a first order transfer function, whichconverts the valve opening command in a valve position. This is givenby:

$\overset{u_{sol}^{cmd}}{arrow}{\frac{z_{sol}^{\max}}{{\tau_{sol}s} + 1}\overset{z_{sol}}{arrow}}$

The transient system behavior is characterized by the time constantτ_(sol) and the position of the needle 6 at the maximum valve opening isgiven by z_(sol) ^(max). Instead of a solenoid valve, a piezoelectricactuation is possible.

Mass Flow Rates

The mass flow rate through each valve is calculated from the standardthrottle equation for liquids, which is:

$\begin{matrix}{{\overset{.}{m}}_{in} = {A_{in}C_{din}{\sqrt{2\rho_{j}{{p_{CR} - p_{IA}}}} \cdot {{sgn}( {p_{CR} - p_{IA}} )}}}} & {{Eq}.\mspace{14mu} 3.1} \\{{\overset{.}{m}}_{bd} = {A_{bd}C_{dbd}{\sqrt{2\rho_{j}{{p_{AC} - p_{JC}}}} \cdot {{sgn}( {p_{AC} - p_{JC}} )}}}} & {{Eq}.\mspace{14mu} 3.2} \\{{\overset{.}{m}}_{zd} = {A_{zd}C_{dzd}{\sqrt{2\rho_{j}{{p_{AC} - p_{CC}}}} \cdot {{sgn}( {p_{AC} - p_{CC}} )}}}} & {{Eq}.\mspace{14mu} 3.3} \\{{\overset{.}{m}}_{ad} = {A_{ad}C_{dad}{\sqrt{2\rho_{j}{{p_{CC} - p_{JC}}}} \cdot {{sgn}( {p_{CC} - p_{JC}} )}}}} & {{Eq}.\mspace{14mu} 3.4} \\{{\overset{.}{m}}_{sol} = {A_{sol}C_{dsol}{\sqrt{2\rho_{j}{{p_{JC} - p_{LP}}}} \cdot {{sgn}( {p_{JC} - p_{LP}} )}}}} & {{{Eq}.\mspace{14mu} 3}\mspace{11mu} 5} \\{{\overset{.}{m}}_{aci} = {A_{aci}C_{daci}{\sqrt{2\rho_{j}{{p_{IA} - p_{AC}}}} \cdot {{sgn}( {p_{IA} - p_{AC}} )}}}} & {{Eq}.\mspace{14mu} 3.6} \\{{\overset{.}{m}}_{ann} = {A_{ann}C_{dann}{\sqrt{2\rho_{j}{{p_{AC} - p_{SA}}}} \cdot {{sgn}( {p_{AC} - p_{SA}} )}}}} & {{Eq}.\mspace{14mu} 3.7} \\{{\overset{.}{m}}_{inj} = {A_{inj}C_{dinj}{\sqrt{2\rho_{SA}{{p_{SA} - p_{cyl}}}} \cdot {{sgn}( {p_{SA} - p_{cyl}} )}}}} & {{Eq}.\mspace{14mu} 3.8} \\{\rho_{j} = \{ \begin{matrix}{\rho_{in}\mspace{14mu}} & {{{if}\mspace{14mu} p_{in}} \geq p_{out}} \\{\rho_{out}\mspace{11mu}} & {\; {{{if}\mspace{14mu} p_{in}} < p_{out}}}\end{matrix} } & {{Eq}.\mspace{14mu} 3.9}\end{matrix}$

Formula Symbols Used:

{dot over (m)}_(in): mass flow rate through each input choke in kg/s

{dot over (m)}_(bd): mass flow rate through the bypass valve betweenstorage chamber 3 and the connection volume 5 in kg/s

{dot over (m)}_(zd): mass flow rate through the feed valve at the inletof the control chamber 2 in kg/s

{dot over (m)}_(ad): mass flow rate through the outlet valve of thecontrol chamber 2 in kg/s

{dot over (m)}_(sol): mass flow rate through the solenoid valve in kg/s

{dot over (m)}_(aci): mass flow rate through the inlet of the storagechamber 3 in kg/s

{dot over (m)}_(ann): mass flow rate through the needle seat in kg/s

{dot over (m)}_(inj): mass flow rate through the injector nozzle in kg/s

Based on the above formulated injector model, the person skilled in theart obtains by means of the observer in a known manner (see, forexample, Isermann, Rolf, “Digital Control Systems”, Springer VerlagHeidelberg 1977, chapter 22.3.2, page 379 et seq., or F. Castillo et al,“Simultaneous Air Fraction and Low-Pressure EGR Mass Flow RateEstimation for Diesel Engines”, IFAC Joint conference SSSC—5th Symposiumon System Structure and Control, Grenoble, France 2013) the estimatedvalue {circumflex over (m)}_(d) and/or {circumflex over (z)} and thestate signal C.

Using the above equation systems, the so-called “observer equations” areconstructed, preferably using a known observer of the “sliding modeobserver” type, by adding the so-called “observer law” to the equationsof the injector model. With a “sliding mode” observer, the observer lawis obtained by calculating a “hypersurface” from the at least onemeasuring signal and the value resulting from the observer equations. Bysquaring the equation of the hypersurface, a generalized Ljapunovequation (generalized energy equation) is obtained. It is a functionalequation. The observer law is that function which minimizes thefunctional equation. This can be determined by the known variationtechniques or numerically. This process is carried out within onecombustion cycle for each time step (depending on the time resolution ofthe control).

The result is depending on the application, the estimated injectedamount of liquid fuel, the position of the needle 6 or one of thepressures in one of the volumes of the injector.

What we claim is:
 1. An internal combustion engine comprising: a controldevice; at least one injector for liquid fuel, which can be controlledby the control device by means of an actuator control signal, whereinthe at least one injector comprises an injector outlet opening for theliquid fuel which can be closed by a needle; and a sensor, by means ofwhich a measurement variable of the at least one injector can bemeasured, wherein the sensor has or can be brought into a signalconnection to the control device; wherein an algorithm is stored in thecontrol device, which algorithm calculates a state of the injector onthe basis of input variables and an injector model, compares the statecalculated by means of the injector model with a target state, andproduces a state signal in accordance therewith, which state signal ischaracteristic of a change in the state of the injector that occursduring intended use of the injector and/or an unforeseen change in thestate of the injector, wherein the input variables comprise at least theactuator control signal and the measurement values of the sensor.
 2. Theinternal combustion engine according to claim 1, wherein the algorithmcomprises a pilot control, which from the desired target value of themass of liquid fuel and/or a needle position target value calculates apilot control signal for the actuator control signal.
 3. The internalcombustion engine according to claim 2, wherein the algorithm comprisesa feedback loop with the actuator control signal calculated by the pilotcontrol and the at least one measurement variable by means of theinjector model, calculates the mass of liquid fuel output throughinjector outlet opening and/or the position of the needle and, ifnecessary, corrects the actuator control signal.
 4. The internalcombustion engine according to claim 1, wherein the algorithm comprisesan observer, which, using the injector model, the actuator controlsignal and the at least one measurement variable, estimates the injectedmass of liquid fuel and or the position of the needle.
 5. The internalcombustion engine according to claim 1, wherein the injector modelcomprises at least: the pressure progressions in the volumes of theinjector filled with the liquid fuel; mass flow rates between thevolumes of the injector filled with the liquid fuel; a kinematicvariable of the needle being a position of the needle relative to theneedle seat; and dynamics of the actuator of the needle, preferablysolenoid valve dynamics.
 6. The internal combustion engine according toclaim 1, wherein the injector comprises at least: an input storagechamber connected to a common rail of the internal combustion engine; astorage chamber for liquid fuel connected to the input storage chamber;a volume over the needle seat connected to the storage chamber; aconnection volume connected on one side to the storage chamber and onthe other side to a drain line; an outlet opening for liquid fuel, whichcan be closed by a needle and is connected to the volume over the needleseat; an actuator controllable by means of the actuator control signalfor opening the needle; and a control chamber connected on one side tothe storage chamber and on the other side to the connection volume. 7.The internal combustion engine according to claim 1, wherein the atleast one measurement variable is selected from the following variablesor a combination thereof: pressure in a common rail of the internalcombustion engine; pressure in an input storage chamber of the injector;pressure in a control chamber of the injector; and start of the needlelift-off from the needle seat.
 8. The internal combustion engineaccording to claim 7, wherein the control device is configured toproduce a state signal which provides information about a deviation ofat least one of the measurement variables relative to a predeterminedvalue.
 9. The internal combustion engine according to claim 1, whereinthe control device is configured to execute the algorithm during eachcombustion cycle or selected combustion cycles of the internalcombustion engine.
 10. The internal combustion engine according to claim1, wherein the control device is configured to execute the algorithmduring each combustion cycle or selected combustion cycles of theinternal combustion engine.
 11. The internal combustion engine accordingto claim 1, wherein the control device is configured to execute thealgorithm during each combustion cycle or selected combustion cycles ofthe internal combustion engine and to statically evaluate the deviationsthat have occurred.
 12. The internal combustion engine according toclaim 1, wherein the control device is configured to determine on thebasis of the state signal a remaining service life of the injectorand/or whether the injector is to be replaced.
 13. The internalcombustion engine according to claim 1, wherein the control device isconfigured to, based on the state signal, a correction of the actuatorcontrol signal and/or the pilot control signal.
 14. A method foroperating an internal combustion engine, in particular an internalcombustion engine according to claim 1, comprising: supplying acombustion chamber of the internal combustion engine with liquid fuel;calculating based on input variables and an injector model, a state ofthe injector; comparing the state of the injector with a target state;and depending on the result, producing a state signal characteristic ofa change in the state of the injector that occurs during an intended useof the injector and/or an unforeseen change in the state of theinjector; wherein the input variables comprise at least the actuatorcontrol signal and the measurement values of the sensor.
 15. A methodfor operating an internal combustion engine, comprising: injectinginjector liquid fuel into a combustion chamber of the internalcombustion engine; calculating, based on inputs variables and aninjector model; a state of the injector; comparing the state of theinjector with a target state; and depending on the result, producing astate signal characteristic of a change in the state of the injectorthat occurs during intended use of the injector and/or an unforeseenchange in the state of the injector; wherein the input variablescomprise at least the actuator control signal and the measurement valuesof the sensor.